In a paper-making process, chemical pulping yields, as a by-product, black liquor, which contains almost all of the inorganic cooking chemicals along with lignin and other organic matter separated from the wood during pulping in a digester. The black liquor is burned in a recovery boiler. The two main functions of the recovery boiler are to recover the inorganic cooking chemicals used in the pulping process and to make use of the chemical energy in the organic portion of the black liquor to generate steam for a paper mill.
In a kraft recovery boiler, a superheater structure is placed in the furnace in order to extract heat by radiation and convection from the furnace gases. Saturated steam enters the superheater section, and superheated steam exits from the section. The superheater structure comprises a plurality of platens.